1. Field of the Disclosure
The embodiments described herein relate to an internal imaging system using the detection of backscatter x-rays and may be used for the internal inspection of railway track components.
2. Description of the Related Art
Currently the detection of many internal flaws of railway track components may be found through either destructive or direct-contact methods. Destructive inspection methods may not be desired as the component, or at least a portion of the component, is damaged and/or destroyed. Direct-contact methods of inspection are typically slow, reducing the amount of track that may be inspected during a single date to detect potential flaws in the railway track components. For these reasons and in order to increase track component inspection productivity, reliability, and accuracy there is a great need for improved automated inspection methods.
Some flaws may currently be detected using a destructive inspection method. For example, a hollow region in a tie can be exposed through a destructive method such as cutting a cross-section with a chain saw. Such a defect is important to find because if a hollow or decayed region of a tie is in the spike area it may comprise the spike holding ability of the tie as well as the load bearing capacity of the tie.
One conventional non-destructive inspection technique is to “ping” the tie by throwing a rock at it, kicking the tie itself, and/or striking it with an object. An inspector tries to determine whether the tie is hollow or not based on the sound created by striking the tie. This assessment is subjective in nature and requires a human tie-by-tie evaluation. Further, the portion of the tie having a void or decayed region may not be struck by the random kicking or hitting of the tie. This method of determining faulty ties may not be highly accurate in determining whether a tie is faulty.
It has been estimated according to one American Railway Engineering Association study that 44% of wood tie failures are due to decay and deterioration that may not be visible from the surface. Other failure modes are estimated at 18-20% plate cutting, 16-18% splitting, 14-16% spike kill, and the remaining by a broad range of additional reasons (termite infestation, etc.). A true objective inspection system would be able to collect both surface and internal images, with the ability to forecast a tie's remaining life accordingly.
There are other examples of railway track component flaws that illustrate the need for an Internal Imaging solution. For example, one flaw is a crack in a concrete tie. Often a crack in a concrete tie may be positioned under the ballast level and thus, a track inspector could easily fail to detect this flaw. Taking the time to remove the ballast, inspect each tie at the sub-ballast level, and then replace the ballast takes far too much maintenance time on a rail line.
Another potential flaw that may be detected by an internal imaging system is Rail Base Corrosion (RBC). Although RBC can be found on any track, it is most prevalent in tunnels and/or where the track is electrified. This may be due to the combination of standing water and electricity flowing through the rail acting to rust and erode the rail-base at an increased rate.
The present disclosure is directed to detecting the above identified problems in railway components with non-destructive means. Other than wood ties, concrete ties, and RBC, it would also be beneficial to detect flaws in fasteners, pads, spikes, plates, composite ties, slab track, bridges, and tunnels.